1. Field of the Invention
The invention pertains to a longitudinal adjustment device on a vehicle seat in which each side of the seat is attached to runner rails, which are mounted so that they are free to slide in guide rails attached to the vehicle, and where each runner rail has a locking device, which can be released from its connection to the guide rail, which locking device comprises a release lever supported with freedom to swivel on each runner rail for moving the device into its released position, this lever being shifted via rods of an actuating element supported on the runner rails.
2. Description of the Related Art
A longitudinal adjustment device of the type indicated above is known from DE 198-27,068 C1, in which the ends of the release levers cooperating with the rods of the actuating element extend at an angle to the horizontal along the associated runner rails. The rods of the actuating element are supported in the bearing seats on the runner rails in such a way that they are able not only to swivel but also to slide in the axial direction. This arrangement makes it possible to compensate for the elasticity of the components in the path along which the forces flow upon actuation of the longitudinal adjustment device by a handle on the seat back, which leads to the direct release of the latching claws on one of the long sides of the seat. As a result of this compensation, the latching claws on the other long side of the seat can also be released. Nevertheless, there is no compensation in the case of the object of DE 198-27,068 C1 for the overstroke which can occur as a result of differences in the manufacturing tolerances at the latching claws.
That is, as a result of manufacturing tolerances, it is possible that the release lever on the left side of the seat must travel a longer distance to release the latching claw than the release lever on the right side of the seat must travel. This means that, when the release levers are actuated via the rods by an actuating element, it is possible that, after the lever has traveled a certain distance, the first latching claw is released and the runner rail becomes free to slide along the guide rail before the latching claw of the locking device on the other side is released. So that this second locking claw can also be released completely from its locked position, the lever must travel a certain additional distance. This is not possible with the known longitudinal adjustment device, because no provisions are made to allow for this overstroke.
In the case of the longitudinal adjustment device known from DE 198-27,065 A1, the elasticity of the actuating element is to be compensated by a spring element mounted on a rod of the actuating element. One end of the spring is attached to the rod, whereas the other end engages with the end of a release lever of a locking device on a runner rail of the seat.
The disadvantage here, however, is that the ability to compensate for manufacturing tolerances is available only on one of the rods of the actuating element. If, as a result of tolerances at the latching claw of the locking element, a certain overstroke is required precisely on the side on which the spring element is provided, the actuating element cannot be actuated to the point of complete release, because the locking element on the other side of the seat may already be located in its end position.
The task of the present invention is therefore to improve a longitudinal adjustment device of the type indicated above in such a way that sufficient compensation for tolerances at the latching claws is ensured along with sufficient compensation of the resulting overstroke, so that the locking device can be released reliably and completely on both rails of the seat.
This task is accomplished in that the adjusting moment exerted on the actuating element is transmitted to the rods via a differential, where the rods are disconnected from each other. According to these features, it is sufficient to provide a means for disconnecting the rods from each other along the route by which the adjusting movement is transmitted from the actuating element to the rods which actuate the release lever of the locking device on the rail. As a result of this measure, a rod which, as a result of tolerances, must travel a greater distance than the other rod before completely releasing the locking device during the adjustment process, can be shifted even farther by way of the actuating element, even if the rod with the shorter adjusting distance has already reached the end position of the locking device and thus cannot be moved any farther. As a result of the measure according to the invention, the goal is therefore achieved that both locking devices on the seat can be moved completely out of their locking position and into the released position by the disconnected rods. In this released position, the seat can then be adjusted longitudinally without friction.
In an advantageous embodiment, the means for disconnecting the rods from each other comprises a lever, which has a swivel axis which is centered with respect to the lever, on which axis one end of the actuating element is supported. The lever, which is supported with freedom to swivel on one end of the actuating element, has two arms, which extend away from the centrally located swivel axis. The radially outer ends of the lever arms are in actuating connection with the rods. When the rods are actuated by the compensating lever via the actuating lever, the two rods are first shifted uniformly downward. After one of the rods has reached its end position, the other rod can still continue to move, because the compensating lever tilts around the swivel axis on the actuating lever, which thus allows the second rod to move further downward until it completely releases the locking device assigned to it.
According to another embodiment, it is also favorable for the rods to be mounted on a transverse tube in such a way that they can both swivel and slide, because as a result it becomes possible to reduce the distance between the two rods when the compensating lever tilts. This swiveling and sliding arrangement prevents the rods from getting jammed on the transverse tube.
The functionality of the rods can be improved even more by mounting them on the transverse tube by way of support tubes, as a result of which the rods are supported on the transverse tube in a way which prevents them from tilting.
In another embodiment of the invention, additional rods are provided at the ends of the two support tubes which face the actuating element. The end of each of these rods passes through an opening in the end of the associated lever arm of the compensating lever and thus enters into a working connection with the compensating lever. AS a result of this measure, the length of the compensating lever can be reduced, and the lever thus acquires greater rigidity.
In another embodiment according to the invention, the differential is designed as a planetary gear system. In this case, the transverse tube is divided into two parts, and these two parts of the transverse tube represent the first and second takeoffs of the planetary gear system. The first takeoff is connected nonrotatably to one of the rods, whereas the second takeoff is connected nonrotatably to the second rod. The two takeoffs, i.e., the two parts of the transverse tube, are supported rotatably one inside the other, so that the two takeoffs are able to rotate relative to each other. The planetary gear system can consist of an internal gear, which is mounted nonrotatably on the one takeoff; a spur gear, which is attached nonrotatably to the second takeoff; and a planet wheel, also supported rotatably between the internal gear and the spur gear. This planet wheel can be supported on the actuating lever, which is itself supported rotatably on a takeoff (a part of the transverse tube) on the spur gear side. In this embodiment of the invention, the two rods can also be disconnected very reliably from each other without the need for a large amount of effort in terms of either material or production work.